As both Dolly Parton (queen of country music) and David Brent (king of the BBC comedy The Office) said: "If you want the rainbow, you gotta put up with the rain".

Enthusiasts for a so-called "rainbow alliance" in Cardiff Bay to turf Labour from power probably don't feel like either singing or laughing at the moment.

They may feel their dream is beginning to fade now that First Minister Rhodri Morgan and Plaid Cymru's Ieuan Wyn Jones are about to begin serious talks on the prospect of going into government together.

Much heat has been generated by the prospect of Plaid teaming up with Labour, rather than with the Conservatives and Liberal Democrats.

But it is worth pointing out that the "rainbow alliance" of the three opposition parties remains very much in contention.

The "All-Wales Accord," a programme for government drawn up by Plaid, the Tories and the Liberal Democrats, is essentially a done deal.

Supporters of the "rainbow option" are putting up with some summer rain on their parade

Although it still needs the backing of Plaid's executive and national council, the indications - before negotiations with Labour re-started - were that that would not be a huge problem.

The "rainbow" is the default position - if Plaid Cymru cannot get a better deal from Labour.

A possible referendum on giving the Welsh assembly Scottish-style law-making powers is the most tempting treat in the box of chocolates Labour leaders are apparently wafting under the noses of Plaid negotiators.

'Getting chummy'

But Mr Morgan has a considerable task ahead to persuade his party's MPs and the wider Welsh Labour family to hold hands with Plaid.

First, Mr Morgan has to convince them it is worth getting into bed with bitter political rivals to keep his administration in office.

Second, he has to persuade them to back a referendum on extending the assembly's powers.

Wales could be in line for a new referendum on the assembly

If there is a yes vote in any referendum the role of Welsh MPs will, of course, be further diminished as more power flows to Cardiff Bay.

Third, to satisfy Plaid's appetite properly, they would need to agree to campaign for a yes vote in that referendum.

That cliché about turkeys voting for Christmas is irresistible at this point.

The last thing Plaid wants is a referendum campaign with half the Labour Party urging a no vote.

A no vote would be disastrous for Plaid's devolution ambitions. The MPs are warning Mr Morgan not to rush or sign blank cheques to stay in office and there is mounting pressure from influential Labour figures for a special party conference to be held to thrash things out.

We also mustn't forget there is also opposition within Plaid to keeping a Labour administration in power.

Plaid's ultimate goal is to replace Labour as the traditional party of government in Wales.

Does it really want to offer a fragile Labour administration a lifeline now? But equally, does Labour want to be the one to offer Plaid the credibility of seats around the Welsh cabinet table?

The journalists, pundits and politicians in Cardiff Bay seem fairly divided on whether the "rainbow" or Lab-Plaid alliance will win through.

Supporters of the "rainbow option" are putting up with some summer rain on their parade at the moment.

Despite all the talk of Labour and Plaid getting chummy, the rainbow hasn't faded from the horizon in Cardiff Bay just yet.